The Earthquakes resolved an immediate need Tuesday by acquiring center back Aaron Pitchkolan of FC Dallas for a conditional draft pick in 2011. But the trade won’t solve all the problems for a struggling team that plays host to the New York Red Bulls tonight and first-place Chivas USA on Saturday.

Six weeks into the season, the Quakes (1-3-2) have yet to fulfill the promise of off-season additions meant to bolster the offense. Because of untimely injuries, missed scoring opportunities and mindless defensive breakdowns, San Jose has earned only one more point (five) than last year’s expansion team did through the first six matches when it went 1-4-1.

The Earthquakes hope to regroup with two matches at Buck Shaw Stadium, starting tonight with a U.S. Open Cup play-in game. Both the Quakes and the Red Bulls will lean on seldom-used reserves in the game that has no bearing on the Major League Soccer standings.

Coach Frank Yallop is more concerned with his depleted backline.

“We just have to make sure we can get through” the week “with just two center backs,” he said Tuesday.

Pitchkolan, a 6-foot-2 back, became an attractive option for the Quakes. Pitchkolan, 26, played his first four seasons in Dallas, where he had a career-best 21 appearances last season.

“We need coverage,” General Manager John Doyle said.

After the Quakes lost defender James Riley to Seattle in the expansion draft, San Jose’s star center back Jason Hernandez suffered a calf strain while training with the U.S. national team last winter. Hernandez hasn’t played for the Quakes this season but could return in a week.

Then Ryan Cochrane was lost for three months after undergoing surgery on his left ankle last week. He had surgeries on both ankles in the off-season but never fully recovered.

Center midfielder Ramiro Corrales is doubtful this week because of an ankle sprain, and left wing Darren Huckerby remains questionable with a quadriceps strain.

The defensive breakdown “shows because we haven’t had a clean sheet all year,” forward Ryan Johnson said of the injured players.

San Jose will need to right itself quickly for fear of falling out of the playoff race. Chivas USA is dominating the Western Conference with 16 points. After Saturday, the Quakes play five of six on the road, where they have failed to score in two games.

“I’m not worried about us scoring goals, because it will happen,” said Johnson, whose open shot Saturday ended up being blocked by Seattle goalie Kasey Keller.

A goal would have tied the score and potentially changed the complexion of a match San Jose lost 2-0.

“It’s like a nightmare,” Johnson said. “When the ball hits your head like that you know it’s going in and all of sudden you see a hand out of nowhere.”

It has been that kind of season for the Quakes so far.

“We’ve not clicked,” Yallop said. “We moved the ball well, we looked dangerous at times, but there is just something that is missing.”